1. The earliest stages or first traces of anything.2. Extant copies of books produced in the earliest stages (before 1501) of printing from movable type.

Quotes:Somewhere in the incunabulum of time the New Year lay awaiting birth. Outside, in the dark, and with none to call it friend, the old year was fading into death. -- Edwin Markham, The real America in romance, Volume 12

Every sane soul is an incunabulum -- David Graham, The grammar of philosophy: a study of scientific method

Origin:Incunabulum derives, in the early printing press industry, from the Latin incuna , "to place a baby in a cradle."

I was disappoointed to learn that the name arises not because of some fancied resemblance between the pages and swaddling-clothes, or the press and a cradle, but just from a general metaphor meaning 'infancy' -- because this was the technique used in the infancy of book-making.